Polymerization of olefins with a chomyl bis(triorganotitanate catalyst

ABSTRACT

CHROMYL BIS(TRIORGANOTITANATES) AND RELATED COMPOSITIONS ARE PREPARED FROM A CHROMIUM OXIDE AND AN ORGANOTITANIUM COMPOUND AND, WHEN COMBINED WITH AN ORGANOALUMINUM COMPOUND, ARE USEFUL FOR THE POLYMERIZATION OF OLEFINS.

United States Patent O 3,752,795 POLYMERIZATION F OLEFINS WITH A CHROMYLBIS(TRIORGANO'IITANATE) CATALYST David E. Boone, Downers Grove, Ill.,assignor to Standard Oil Company, Chicago, Ill. No Drawing. Filed Mar.24, 1972, Ser. No. 237,922 Int. Cl. C08f 1/42, 3/06 US. Cl. 260-882 RClaims ABSTRACT OF THE DISCLOSURE Chromyl bis(triorganotitanates) andrelated compositions are prepared from a chromium oxide and anorganotitanium compound and, when combined with an organoaluminumcompound, are useful for the polymerization of olefins.

SUMMARY OF THE INVENTION This invention relates to the catalyticpolymerization of olefin hydrocarbons and more particularly to a processand catalyst therein for the polymerization of terminally unsaturatedhydrocarbons. Still more particularly, the invention relates to apolymerization process utilizing a catalyst ssytem comprising anorganoaluminum compound and novel chromium-organotitanate compositions.

In accordance with the instant invention, olefins are polymerized tonormally solid polymers at atmospheric pressure and above and atmoderate temperatures and above with a catalyst system comprising (a) anorganicsolvent-soluble composition prepared by reaction of anorganotitanate with a chromium oxide at elevated temperatures in aninert solvent and, (b) an organoaluminum compound. The molecular weightdistribution of the polymeric products formed by contacting an olefinwith the above combination may be varied by changing the chromium totitanium ratio used.

BACKGROUND OF THE INVENTION US. Pat. 3,474,080 discloses the utility ofchromyl bis(organophosphates) combined with organoaluminum compounds asolefin catalysts, but shows only compounds containing a singletransition element. South African patent application 662,674 disclosesthe use of silylchromates combined with alkyl aluminum alkoxides for thesame purpose, but again compounds containing a single transition elementare described.

Now it has been found that by preparing an organicsolvent-solublecomposition in which two transition elements are present and activatingit by an organoaluminum compound, olefins may be polymerized bycontacting them with said compositions to form polymers havingcontrollable molecular weight distributions.

STATEMENT OF THE INVENTION In the process embodied herein, the catalystsystem comprises (a) an organoluminum compound and (b) a compound of theformula:

wherein R is a hydrocarbon radical, e.g., alkyl, alkaryl, aryl,cycloalkyl, or the like, or combinations thereof. As specific examplesof compounds falling within the scope of the aforesaid formula anduseful for the practice of this invention are the following: chromylbis(tributyltitanate), which is prepared from tetrabutyltitanate;chromyl bis(tricyclohexyltitanate), which is prepared fromtetracyclohexyltitanate; chromyl bis(triphenyltitanate), which is madefrom tetraphenyltitanate, chromyl bis(tribenzyltitanate), which is madefrom tetrabenzyltitanate;

ice

chromyl bis(tritolyltitanate), which is made from tetratolyltitanate.Especially preferred are compositions prepared from the tetraalkylderivatives.

This novel composition of the instant invention is prepared by reactinga tetraorganotitanate of the formula (RO) Ti, wherein R is defined asabove, with a chromium oxide at an elevated temperature in an inertsolvent. Preferably, chromium (VI) oxide is used.

The reactants are heated in any suitable solvent that is resistant tooxidative attack by the chromium oxide. Examples of solvents includemethylene chloride, carbon tetrachloride, chloroform, hexane, octane,cyclohexane, and decahydronaphthalene, and mixtures of these. In generalthe solvent is a saturated hydrocarbon of the halogenated, alkyl, orcycloalkyl variety having a reflux temperature between about 15 C. andabout C. at 1 atmosphere.

Although the chromium oxide, preferably chromium trioxide, and thetetraorganotitanate are reacted preferably in a mole ratio of about 5:1to about 1:2, it is possible to use a ratio of chromium trioxide to thetitanate of about 6:1 up to about 1:4. Any proportion lower than about1:4 gives a small amount of usable product while anything above about6:1 is wasteful of the chromium trioxide. The solvent is employed in thereaction in an amount suflicient to give a total concentration of about0.1 to 5.0 moles with respect to the reactants in the reaction vessel.

When greater than a 1:2 mole ratio of chromium oxide, preferably CrO to(RO) Ti is used, it is presumed that a substantial proportion ofpolymeric material of the general formula:

\t a... l.

is formed. However, if x in the above formula is larger than about fiveor six, the material is too insoluble in the organic solvent used forpolymerization.

The reaction time can vary from a few minutes up to twenty-four hours orlonger, but the usual reaction time for a high yield is approximatelyeight to twenty-four hours. The yield increases with time of reactionand is limited by the amount of reactants used.

The reaction temperature varies depending upon the solvent selected;however, a reflux temperature between about 15 C. and 90 C. ispreferred. For example, when the solvent is carbon tetrachloride, thereaction temperature is about 77 C. at 1 atmosphere pressure.

In reference to the organoaluminum compound that is the other componentof the catalyst system embodied herein, particularly suitable andpreferred is a trialkylaluminum, such as triethylaluminum, tripropylaluminum, triisobutyl aluminum, tri-n-decyl aluminum, and the like anddialkyl aluminum halides such as diethyl aluminum chloride.

The amount of the organoaluminum compound used depends upon the amountof the titanium-chromium composition used. Usefully, the organoaluminumcompound mixed-transition-metal composition ratio varies from about 0.1to about 5:1. More preferably, it varies from about 0.5 to about 3:1and, most preferably, a ratio of 1 to 3:1 is desired.

Reaction conditions at which the polymerization may be carried out withthe novel catalyst system include the following: A temperature of about0 C. to about 250 0, preferably, about 20 C. to about 110 C., mostpreferably, about 20 C. to about 90 C., is used. A pressure of about 40p.s.i.g. to about 5,000 p.s.i.g., preferably, about 60 p.s.i.g. to about1,000 p.s.i.g., most preferably, about to about 700 p.s.i.g., is used.

The total catalyst concentration is not critical, but usefully is about0.01 to 5 grams of catalyst product per liter of solvent in the reactionvessel or about 0.001 to 1.0 percent, based on the weight of the olefinused. By total catalyst is meant here the titanium-chromium compositionplus the organoaluminum compound.

A chain terminating agent such as hydrogen is advantageously used withthe instant compositions during polymerization since its eifect on themolecular weight distributions of the polymers prepared may becontrolled by controlling the titanium to chromium ratio in thecatalyst. The molecular weight of the resulting polymer usingchromium-based olefin catalysts is considerably less affected byhydrogen than the molecular weights of polymers produced bytitanium-based olefin catalysts.

The titanium-chromium compositions of the instant invention can be usedeither in solution or as a solid, alone or supported on an inert supportmaterial such as alumina or silica. In either of the above physicalforms, it can be used also in a slurry (particle form) process or atmore elevated temperatures in a solution form process or to polymerizeolefin directly from the liquid state (bulk type of process) or thevapor state. Preferably, it is used in solution to polymerize olefins ina solution type or particle form type of process.

It is preferred that the selected reaction medium be essentially free ofimpurities which may react to destroy catalyst activity or whichcopolymerize with the olefinic hydrocarbon; that is, appreciablequantities of materials such as carbon dioxide, oxygen, and acetyleniccompounds should preferably be absent.

Monomers within the contemplation of this invention are ethylene andterminal olefins containing 3-10 carbon atoms and diolefins such asbutadiene.

For this process the polymerizable hydrocarbon may be used insubstantially pure form, or there may be used a mixture containing majorquantities thereof, provided no impurities are present in substantialamount to destroy the catalyst and/or contaminate the polymer products.For instance, ethylene obtained by the cracking of hydrocarbon streamsis satisfactory if acetylenic and oxygenated materials are not presentin more than trace amounts.

In carrying out the polymerization process described herein, it ishighly desirable to maintain the polymerization zone free of extraneousgases. This can be done by keeping the reactor blanketed at all timeswith an inert gas, e.g., operating with an inert gas such as nitrogen,argon or helium. Preferably, the reactor and its contents are blanketedwith the polymerization substance, e.g., ethylene gas, to avoidunnecessary dilution of the reactor contents with inert gases.

To describe the invention further, the following examples set forthspecific embodiments of catalyst systems embodied herein forpolymerizing olefins to high molecular weight polymers. In theseexamples inherent viscosities were measured in Decalin at 135 C. at aconcentration of 0.1 gram per 100 milliliters of solvent. Hexaneextractables were measured using a Soxhlet type of extraction process.Annealed densities were measured after the sample was slowly cooledovernight from 150 C. Melt indices were measured according to ASTMD1238. All molecular weight, MW and Mn values were obtained by gelpermeation chromatography.

EXAMPLE I In a typical catalyst preparation reaction, 2.0 grams ofanhydrous chromium trioxide was placed in 120 milliliters of carbontetrachloride and 15 milliliters of tetra butyltitanate was added. Thesystem was heated to reflux for twenty-four hours with stirring. Thegreen reaction mixture was filtered to remove the unreacted chromiumtrioxide. Care was taken throughout to eliminate water from the system.Desirably, light should be kept away from the reaction mixtu e and pructs.

4 EXAMPLE H For the polymerization of ethylene, 2 milliliters of thefiltered catalyst reaction mixture of Example I was added to 180milliliters of polymerization grade hexane in a Fisher Porter bottle.While stirring, 2.6 millimoles of aluminum triethyl was introduced (allwork was done under argon). The reaction vessel was fitted with apressure head and the system was heated to 70 C. Ethylene was introducedto a total system pressure of 100 p.s.i.g. The reaction temperature wasmaintained at C. during the one hour reaction period. On termination ofthe reaction, 4.9 gram sof polyethylene was removered.

EXAMPLE III EXAMPLE 1V Under an inert atmosphere, 5.55 grams of reagentgrade anhydrous chromium trioxide was added to 100 milliliters of drycarbon tetrachloride in a flask. A 3.7 milliliter portion oftetrabutyltitanate was added and with stirring the mixture was heated atreflux for seventy-two hours. The green reaction mixture was cooled andthe supernatant liquid was separated from unreacted chromium trioxide bysyringing. The solution was more viscous than in Example III.

EXAMPLE V A 4.01 gram portion of reagent grade anhydrous chromiumtrioxide was added to a flask containing milliliters of dried carbontetrachloride. A 7.5-milliliter portion of tetrabutyltitanate was addedand the mixture was heated at reflux for eighteen hours. The greenreaction mixture was cooled and the liquid layer was separated from theunreacted chromium trioxide by syringing.

EXAMPLE VI Under an inert atmosphere, a 4.45 gram portion of reagentgrade anhydrous chromium trioxide was added to 90 milliliters of driedhexane in a flask. With stirring, 8.3 milliliters of tetrabutyltitanatewas added and the reaction mixture was heated at 63 C. for twenty-fourhours. After cooling, the green solution was syringed into another flaskto separate it from the unreacted chrc mium trioxide.

EXAMPLE VII A 1.93-gram portion of reagent grade magnesium hydroxidepowder was dried for twenty-four hours at 220 C. in a muifle furnace.This was added to 40 milliliters of dried hexane in a flask under aninert atmosphere. An 8.0-milliliter portion of the reaction mixture ofExample V was added and with stirring this mixture was heated to 60 C.for eighteen hours. After cooling, the solid was washed with hexane. Thesolid remained green after one washing.

EXAMPLE VIII (A) Preparation of the AlCl -Mg(OI-I) support A 4.01-gramportion of reagent grade magnesium hydroxide powder was mixed with 6.18grams of reagent grade anhydrous aluminum chloride at room temperature.The mixture was then heated at C. for eighteen hours. The hard reactionproduct was broken into small pieces and ball-milled for twenty-fourhours.

(B) Preparation of the supported catalyst A 2.0-gram portion of the AlCl-Mg(OH) product from part A was placed in a flask with 45 milliliters ofdried xylene. To this was added milliliters of the reaction product fromExample V. The mixture was heated to 90 C. for six hours with stirring.The reaction mixture was coled and the solid was washed with 40milliliter aliquots of dried hexane six times.

EXAMPLE IX Into a SOD-milliliter, dried rocking bomb was charged 150milliliters of hexane under 50 p.s.i.g. of a feed gas containing 2 molepercent hydrogen and 90 mole percent ethylene. The system was slowlyvented and at atmospheric pressure, a 2-milliliter portion of thecatalyst solution of Example III was introduced. The system was closedand 2.7 millimoles of triethylaluminum in 30 milliliters of hexane wascharged under feed gas pressure. With the reaction mixture temperatureat 78 F., the system was pressured to 320 p.s.i.g. There was animmediate temperature rise to 90 F. The pressure was maintained at400-430 p.s.i.g. throughout the one hour and forty minute reaction time.The reaction temperature was slowly increased to 180 F.

A 33-gram amount of polymer was formed. The inherent viscosity of thepolymer was 2.6. The product contained 4.2 weight percent hexaneextractables after five hours of extractions.

EXAMPLE X A 500-milliliter, stainless steel, stirred reaction was driedat 100 C. for one hour, cooled and evacuated. The vacuum was broken bypressuring 174 milliliters of dry hexane into the reaction with 200p.s.i.g. of ethylene. The hexane was stirred and cooled to roomtemperature and the system was then vented to atmospheric pressure. A1.0-milliliter portion of the catalyst solution of Example III wasadded. The system was closed, pressured to 50 p.s.i.g. with ethylene,stirred for one minute, and vented to atmospheric pressure. A 2.0millimole amount of triethylaluminum in 10 milliliters of hexane wasadded. The system was sealed and pressured to 585 p.s.i.g. withethylene. The temperature slowly rose to 74 C. during thepolymerization. After 1.5 hours, the system was vented.

A 63-gram amount of polymer was recovered. The polymer had an inherentviscosity of 11, an unannealed density of 0.949 gram per milliliter andan annealed density of 0.957 gram per milliliter. After extracting sixhours with hexane, the product showed a 6.8 percent weight loss.

EXAMPLE X'I A 500-milliliter, stainless steel, stirred reactor washeated at 100 C. overnight with a nitrogen purge. The system wasevacuated and cooled at 24 C. The vacuum was broken by pressuring 174milliliters of dry hexane into the reactor with 200 p.s.i.g. ofethylene. The system was vented to atmospheric pressure and 1.0milliliter of the catalyst solution was introduced. (This solution wasthe same as but only 0.1 as concentrated as that used in Example X.)This solution was stirred for two minutes and 0.39 millimole oftriethylaluminum were introduced. The system was immediately pressuredto 580 p.s.i.g. with ethylene. The reaction temperature rose from 24 C.to 38 C. during the one hour forty minute reaction.

An 11.0-gram amount of polymer was recovered. The product showed aninherent viscosity of 27, an unannealed density of 0.948, an annealeddensity of 0.960 and contained 5.5 weight percent hexane extractablesafter five hours.

EXAMPLE XII A 500-milliliter, stainless steel, stirred reactor washeated overnight at 135 C. with a nitrogen purge. The system wasevacuated and the vacuum was broken by charging 160 milliliters of driedhexane pressured with 50 p.s.i.g. of ethylene. The temperature of thesolution was vented to atmospheric pressure. An 0.5-milliliter portionof the catalyst from Example V was introduced followed by 1.9 millimolesof triethylaluminum in 10 milliliters of hexane. The system wasimmediately pressured to '600 p.s.i.g. with ethylene. The reactiontemperature was slowly increased to 88 C. during the 1.5 hour run.

A 6.49-gram amount of polymer was recovered. The polymer had an inherentviscosity of 115.

EXAMPLE XIII A SOO-milliliter, stainless steel, stirred reactor washeated at about C. for three hours with a nitrogen purge. The system wasevacuated and the vacuum was broken by charging milliliters of driedhexane with 50 p.s.i.g. of ethylene. The temperature of the solution wasstabilized at 27 C. and the system was vented to atmospheric pressure.About 40 milligrams of the catalyst from Example VIlI was added followedby 0.15 millimole of triethylauminum. The system was then pressured to600 p.s.i.g. with ethylene. The reaction temperature was slowlyincreased to 82 C. during the one hour run.

A 3.9-gram portion of polymer was recovered.

EXAMPLE XIV A 500-milliliter, stainless steel, stirred reactor washeated at 127 C. overnight with a nitrogen purge. The system wasevacuated and the vacuum was broken by charging 160 milliliters of driedhexane with 50 p.s.i.g. of ethylene. The temperature of the solution wasstabiliZfid at 71 C. and the system was vented to atmospheric pressure.About 14 milligrams of the catalyst from Example VIII was added to thereactor followed by an 0.8 milliliter of a solution containing 0.15millimole of tri ethylaluminum. The system was pressured to 600 p.s.i.g.with a feed gas containing 25 mole percent hydrogen and 75 mole percentethylene. After six minutes this was switched to 100 percent ethylenefed on demand at 600 p.s.i.g. The polymerization temperature wasmaintained at 82 C. during the one hour run.

A 15.2-gram amount of polymer was recovered for a yield of '1,080 gramsof polymer per gram of catalyst. The polymer product had an inherentviscosity of 2.4, an unannealed density of 0.959, an annealed density of0.973, a melt index of 0.5 gram per 10 minutes and a Mw/Mn of 7.0.

While the invention has been described in conjunction with specificexamples, it is to be understood that these are for illustrativepurposes only. Many alternatives, modifications and variations will beapparent to those skilled in the art in light of the foregoingdescription, such alternatives, modifications and variations fallingwithin the spirit and scope of the appended claims.

Having thus described the invention, what is claimed is:

1. A polymerization process which comprises contacting an olefin with acombination of (a) a compound of the formula:

wherein R is selected from the group consisting of alkyl, alkaryl, aryland cycloalk'yl radicals and (b) an aluminum trialkyl or dialkylaluminum compound.

2. The process of claim 1 wherein R is selected from the groupconsisting of cyclohexyl, benzyl, phenyl and tolyl radicals.

3. The process of claim 2 wherein said olefin is ethylene, propylene ormixtures thereof.

4. The process of claim 1 wherein R is butyl.

5. The process of claim 4 wherein said olefin is ethylene, propylene ormixtures thereof.

7 6. A polymerization process which comprises contacting an olefin witha combination of (a) a compound of the formula:

wherein x is integral number between one and about six, inclusive, ormixtures thereof, and wherein R is a hydrocarbon radical selected fromthe group consisting of alkyl, alkaryl, aryl and c'ycloalkyl radicalsand (b) an aluminum trialkyl or dialkyl aluminum compound.

7. The process of claim 6 wherein R is a hydrocarbon radical and isselected from the group consisting of cyclohexyl, benzyl, phenyl andtolyl.

8. The process of claim 7 wherein said olefin is ethylene, propylene ormixtures thereof.

References Cited UNITED STATES PATENTS 3,474,080 10/1969 Rekers 26094.9B 3,493,554 2/1970 Rekers 260-949 B 3,324,101 6/1967 Baker et al.260-949 B JAMES A. SEIDLECK, Primary Examiner E. I. SMITH, AssistantExaminer U.S. Cl. X.R.

25243l R; 26093.7, 94.3, 94.9 B, 429.5

0 UNITED STATES PATENT OFFICE CERTIFICATE OF "CORRECTION Patent No. 3,75,795 Dat d August lb, 1973 I fl David E. Boone It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected 'a shown below;

Column 1, Line 2 ssystem should be system Column 1, Line 57organol'uminum should be changed to organoaluminum Column Line 13 gramsof should be grams of Column l, Line 'l3 removered should be recoveredColumn 5, Line 7 coled should be cooled,

Column 5, Line 7 milliliter should be milliliters Column 5, Line 28--extractions should be extraction Column 5, Line 56 at should bechanged to Y'to" Column 6, Line 21 triethyllauminmn should betriethylaluminum "Sig nediand sealed this 17th clay of September 1974.

(SEAL) Attest: I I McoY GIBSON JR. c, MARSHALL DANN Att'es'ting OfficerI Commissioner of Patents

